Aircraft may include various types of turbomachines to implement various functions. For example, many aircraft include turbomachines to function as the main propulsion engines. The main propulsion engines, in many aircraft, not only provide propulsion for the aircraft, but may also be used to drive various other rotating components such as, for example, generators, compressors, and pumps, to thereby supply electrical and/or pneumatic power. However, when an aircraft is on the ground, its main engines may not be operating. Moreover, in some instances the main propulsion engines may not be capable of supplying the power needed for propulsion as well as the power to drive these other rotating components. Thus, many aircraft include one or more additional turbomachines to function as auxiliary power units (APUs). The APUs, when included and operational, supplement the main propulsion engines in providing electrical and/or pneumatic power. An APU may also be used to start the propulsion engines.
No matter the function of an aircraft turbomachine, it is typically supplied with lubricant from a lubrication supply system, to lubricate various components within the turbomachine. Many of these components, such as main shaft bearings, cannot tolerate relatively long periods of lubricant interrupt. Thus, because aircraft may experience various maneuver conditions within the aircraft flight envelope, some of which may be relatively extreme for certain aircraft, the lubrication supply systems in aircraft are typically designed to maintain adequate lubricant flow to the turbomachines throughout the flight envelope.
Various methods have been and are currently employed to maintain adequate lubricant flow throughout an aircraft's flight envelope. These methods include the use of accumulators, oil-mist systems, check valves, and movable/flexible oil pickup tubes, just to name a few. Although generally safe, reliable, and robust, these methods do present certain drawbacks. For example, these methods can be relatively complex, heavy, and costly to implement.
Hence, there is a need for a system and method of improving aircraft turbomachine tolerance to at least momentary low or no lubricant flow that is not too expensive, complex, and/or heavy. The present invention addresses at least this need.